Polyvinyl acetal resin plastic



mailed July 19.1938 i it h I UNITED STATES PATENT OFFICE Joseph D. Ryan, Toledo, Ohio, assignor to Libbey- Owens-Ford Glass Company, Toledo, Ohio, a corporation of Ohio No Drawing. Original application May 3, v1931, Serial No. 140,428. .Divided and .this application May 14, 1937, ,Serial N? 11%"21525 lates to plais'ticization acetal resin which is not unduly susceptible to v The present inventionre of polyvinyl acetal resins and also to the use water. Polyvinyl acetalresins, not unduly susof the resulting plastics as an interlayer in lamceptible to water, can. be formed usingthe aldeinated safety glass. This is a divisional of my hydes above set forth when condensation with application Serial No. 1'40,428,'filed May 3, 1937. the polyvinyl alcohol or partially hydrolyzed 5 The polyvinyl acetal resins may be formed by polyvinylacetate is carried to a point where at reacting an aldehyde with either a completely least 65 to 70 percent of the alcohol groups ,presor partially hydrolyzed polyvinyl ester. These ent have reacted with the aldehyde. resins can be produced in various ways, the gen- .In the manufacture of laminatedfisafety glass eral practice being to employ polyvinyl acetate for example, it is preferable to employ a plastic and to then either partially or completely *hylnterlayerthat isnot particularly water or moisdrolyzethe same; partially hydrolyzed polyvinyl ture susceptible,thus avoiding. the problem of :acetate being formed when the resultant prodprotecting the marginal, portions of the lamid polyvinyl alc onated safety glass with a weather-proof seal.

uct contains acetyl groups, an I I xhol resulting when the polyvinyl acetate is com- In other fields of use, polyvinyl .acetal resins pletely hydrolyzed. Either of these two submay, under some circumstancesflbesatisfactory stances .,can then be reacted with an aldehyde, even though they be somewhat susceptible to the,

usually in the presence of a mineral acid catalyst, actionof water. to give a condensation'pro'duct termed polyvinyl The present invention I is primarily, concerned acetal resin. with thepreparation of plasticsfrom-thepoly- It willbe understood that v ariqus techniques vinyl acetal resins by incorporating a plastior processes can be employed in getting the lilcizer or plasticlzer mixture with the resin in lastic capable. of sat,-

timate polyvinyl acetal reslneand that this invensuitable amounts to give a, p

ed with the parisfactory service in its .intendeduse. .Polyvinyl.

acetal resins are today available on the open 5 tion is not in any way concern ticular method or methods employed in the probe well to market and there are known plasticizersfor such For example, the esters .of phthalic acid,

duotion of the raw resin. It may point out, however, that the molecules of both resins. I

the toluene sulfonamids, the higher estersotthe of the well known the, partially hydrolyzed polyvinal acetate and the polyvinyl alcohol contain vinyl alcohol glyc ls P y e so groups, and during the reaction step with the plasticizers for these materials. However, .somego aldehyde, the aldehyde condenses with some of of these known plasticizers for this type of resin impair or completely destroy the desirable latent hile other known. plasthe vinyl alcohol groups present, resulting in ticizers give only fair results. I have found that .the polyvinyl acetal resin formation. Most of properties of the resin w my plasticization work in connection with the 7 present invention hasbeen carried on using polyby using specially designed and prepared plasvinyl resins in whichformaldehyde, butyraldeticizers, extremely satisfactory plastics can be hyde. and acetaldehyde, have been employed, 2.1- made from the polyvinyl actal resins which are though it has been my observation that polyunusuallywell suited for employment in the lame ,vinyl acetal resins made by the use of higher inated safety glass field. Considering the large molecular weight aldehydes, such as heptaldenumber of plasticizers now marketed-in sub-. hyde, octaldehyde, benzaldehyde, etc., resemble stantiai quantities, it. is surprising that of the ithe butyraldehyde resin in their plasticization hundreds of plasticizers studied and tested, so characteristics. many were found unsuitable, especially for plas- The extent of reaction of the aldehyde with ties to be employed in the manufacture of lamthe vinyl alcohol groups present in the molecules inated safety glass. However. as will appear 5 of the polyvinyl alcohol or the partially 1137- h r in fter. ther mus 'of n s y b a large drolyzed poiyvinal acetate has a bearing not only number of rigid stipulations placed on a .mateon the yield of polyvinyl acetal resin from :the rial to be used as a plasticizer or these resins, mix, but the degree of condensation must proand it thus becomes obvious that to find ,or to coed beyond a certain point to give a polyvinyl prepare a plasticizer having all of these essen o0 cially for plasticization of the polyvinyl tial characteristics is far from a simple matter, and in fact this resulted in extensive study on my part of new materials most of which were not commercially available at the time I commenced my research work on this subject.

Where the resin is to serve as the plastic interlayer in safety glass, it must be stable to heat and light energy and must have a sufliciently high boiling point and low vapor pressure that the plastic will not bubble or be otherwise unstable when subjected to the varying temperatures encountered in normal use. As has already been mentioned, if laminated safety glass is made from the resin and no edge seal is used to protect the resin, the plasticizer as well as the resin must show adequate resistance to hydrolysis under the conditions of normal usage. The plasticizer must be such that the plastic with, when bonded between glass sheets, will exhibit sufilcient resistance to impact at varying temperatures (normally high, medium, and low temperatures as within a range from about 0 F. to 120 F.). As a further consideration, the plasticizer must not so affect the resin that the interlayer formed therefrom will be too soft at the higher range of temperatures or too brittle at the lower range of temperatures.

To be satisfactory, the plasticizer must be such that it will not unduly exude or sweat out from the plastic and certainly must not in any Way adversely interfere with the adhesion of the plastic layer to the glass, whether the plastic be bonded directly to theglass or throughthe intermediaryof an adhesive material. The properties of the plasticizer must be such that slight variatlons in the ratio of plasticizer to resin,

which normally exist as a result of the plastic manufacture and subsequent storage thereof before use, will not seriously affect the breaking strength of the laminated safety glass at the varying temperatures to which it is exposed. Also, the plasticizer must be suitably compatible that it will not interfere with the resins are used in safety glass or elsewhere.

I have been experimenting with plasticizers for the polyvinyl acetal resins over a period of years. In fact, I have endeavored to approach plasticizer developments not in a haphazard, hit and miss way, but rather by careful and well thought was therefore found necessary to begin the prepation of a new series of materials designed espeacetal resins. On the basis of practical experimental work, as well as a theoretical analysis of the problem, I concluded that a plasticizer of long carbon chain configuration should be the preferred type of plasticizer. I was influenced in Dart in this attempt to produce a long straight chain plasticizer by the long chain characterresin itself, a plasticizer having a similar struc ture should be well suited as compared to the other plasticizers previously tried and lacking in this general characteristic.

Having first decided to develop a plasticizer having a long carbon chain configuration, it was then necessary to give consideration to the kind of materials that might possibly serve in the production of such plasticizers, and I elected to experiment with the straight chain dicarboxylic acids by producing esters therefrom and then'utilizing these esters as plasticizers.

Discouraging results wereat first encountered with the esters of the dicarboxylic acids as plasticizers for the polyvinyl acetal resins. Extensive work, however, in face of these discouraging results, showed that not all of the dicarboxylic acids have a sufficiently long chain structure to give the benefits sought after. For example, the oxalic, malic, succinic, and glutaric acid esters were prepared and tested and found to be lacking in suitable properties. After a great deal of detail experimental work and testing, I concluded that although these were straight chain dicarboxylic acids, they did not include a suflicient number of methylene groups or, stated differently, the chain was not long enough. It was not until'the esters of adipic acid were prepared and tested that outstandingly satisfactory results were realized.

The general formula for these straight chain dicarboxylic acids may be written as follows:

For oxalic acid X equals For malic acid X equals For succinic acid X equals For glutaric acid X equals For adipic acid X equals acid X equals 12 Based on the work done, I am satisfied that the members of the series of straight chain dicarboxylic acids containing less than four methylene groups are'unsatisfactory for the plasticization of the polyvinyl acetal resins. I have likewise established that esters of the straight chain dicarboxylic acids containing four or more methylene groups are preeminently suited for plasticization of the polyvinyl acetal resins. as most of these acids are not available on the open market, and especially as I wanted to be sure of the purity of the plasticizers produced, I prepared most of my own acids and then produced the esters from such acids.

To illustrate methods of preparing the acids, any one of the several methods outlined below can and has been used in preparing the acids:

(1) By oxidation of a straight chain glycol or hydroxy mono carboxylic acid to the corresponding dicarboxylic acid. This method was found to be especially suited for the lowest members of the series. For example, in the case of adipic acid, good yields were obtained by resorting to the oxidation of cyclohexanol.

@WJODUIDOJMHQ Inasmuch 13 won,

4 Electrolysis 8 (2) By electrolysis of the mohoester mono alkali salt of a dicarboxylic acid. To illustrate, a mono alkyl ester of potassium adipate was successfully electrolyzed to yield sebacic acid esters.

COOK 100a C 0 O R dialkyl ester of sebaclc acid COOR

(3) By reduction of the dialkyl ester of a straight chain dicarboxylic acid ester with metallic sodium to the corresponding glycol, replacement of thehydroxyl groups of the glycol with halogen, substitution of the halogen by cyano groups followed by hydrolysis. By following this method, a dicarboxylic acid, having two more carbon atoms than the parent dicarboxylic acid, is obtained. For example, starting with dibutyl sebacate, I obtained decamethylene dicarboxylic acids in good yields as follows:

COOC Hn CH2OH CHIBI I I C H2 Na C H: H Br C HI Reduction (L L 8 8 OOC H9 HzQH H113! dibutyl sebacate CliIzC N $0 OH NaCN H20 CH CH:

H23 4 L 8 i 10 C 10 N O OH Decamethylene dlcerboxylic acid I found the latter two methods especially suited for the preparationof the higher molecular weight dicarboxylic acids.

Esterification of these dicarboxylic acids does not oifer any particular problem. To prepare the esters, the acid is mixed with dry hydrogen chloride gas and the mixture refluxed for several hours. The ester so formed was then purified by washing, drying, and vacuum distillation. In

some cases it was found possible to obtain good yields of a satisfactory product by simple fractionation of the refluxed reaction mixture. My observation indicates that the esters so formed are highly stable compounds which are resistant to hydrolysis and stable to heat and light energy.

The most .common forms of commercially available polyvinyl acetal resins, as previously stated, are those made with formaldehyde, acetaldehyde, or butyraldehyde. 'The polyvinyl acetal resin made with formaldehyde in the reaction step has been found, as might be expected, to be anomalous in its plasticization behavior to the polyvinyl acetal resins made with higher molecular weight aldehydes. Stated differently, thus far in my development work, I have found that anymatcrial suitable as a plasticizer for the polyvinyl acetal resin made using formaldehyde will likewise plasticize the polyvinyl acetal resins made using acetaldehyde, butyraldehyde, and other higher molecular weight aldehydes, but

many of the plasticizers for the latter mentioned polyvinyl acetal resins will not give suitable results as plasticizers for the formaldehyde type of resin.

I have prepared some esters of the straight chain dicarboxylic acids which will plasticize equally well the formaldehyde polyvinyl acetal resin or the other types of polyvinyl acetal resins but, on the other hand, some of the ester plasticizers produced from these long chain acids are incompatible with the formaldehyde type of resin unless blended with other wholly compatible plasticizers such as the dimethyl and diethyl esters of phthalic acid. Certain of the other esters of the dicarboxylic acids have not been successfully used alone, and further I have not found suitable blending plasticizers to make them compatible with the formaldehyde type of polyvinyl acetal resin.

The dimethyl and diethyl esters of the straight chain dicarboxylic acids, having four to six methylene groups, can be used as the sole plasticizer for the polyvinyl acetal resin made using formaldehyde, yielding clear, tough, transparent masses. on the other hand, the dimethyl and diethyl esters of the dicarboxylic acids, having more than six methylene groups, must be blended with a wholly compatible plasticizer for this resin, dimethyl and diethyl phthalates being capable of use in this connection. The proportions of phthalate esters which must be added to obtain clear, tough, resinous plastics vary somewhat, but in general an equal mixture works satisfactorily.

Likewise, I have found that when this series of acids is esterified with higher molecular weight monohydric alkyl alcohols, such as propyl, butyl, amyl, etc., the resultant compounds are not compatible with the formaldehyde type resin except in very small proportions, and in fact in such small proportion that the resultant plastic masses are not greatly superior to the resin plasticized with phthalate esters alone. Further, my work has shown that when this series of acids is esterified with more complex alcohols containing ether groups, such as monomethyl and monoethyl ethers of ethylene glycol, the resulting plasticizers are entirely compatible with thepolyvinyl acetal resins produced using formaldehyde. This unexpected compatibility may be explained by the solvent action contributed to the plasticizer molecule by the addition of the two ether groups.

In general practice where the plastics are to be subjected to varying temperatures and par ticularly the higher temperatures, I prefer to use" as acetaldehyde, butyraldehyde, heptaldehyde,

octaldehyde, etc., I have found that all the esters made from the monohydric alkyl alcohol, such as methyl, ethyl, propyl, butyl, amyl, and octyl, work satisfactorily as plasticizers. Theesters formed from this series of dicarboxylic acids with more complex alcohols, such as alkoxy alkyl alcohols. also work satisfactorily with these resins.

By following the teachings of the invention herein disclosed and as indicated by the data given, a flexible and wide choice of plasticizer selection is made possible. In general, it is obviously desirable to use the acid having the lowest cost and to esterify this with the most inexpensive available alcohol of higher molecular weight. The use of the high molecular weight alcohol reduces the cost or the esteriflcation step and likewise yields an ester plasticizer of higher boiling point and lower vapor pressure, both being sought for properties. Some of the esters of the higher molecular weight acids (especially those containing more than nine methylene groups) were found to be solids, but this change in physical state in no way impaired the efficacy of my results.

As an example of a polyvinyl acetal resin used by me, the following data are given:

Polyvinyl acetate having a viscosity of 15 centipoises in a molar benzene solution at 20 C. was hydrolyzed to the extent of 95%. This partially hydrolyzed polyvinyl acetate was then reacted with formaldehyde in the presence of a catalyst to the point that approximately 90% of the hydroxyl groups present in the molecule were condensed with the aldehyde, giving a resin analyzing as follows:

Percent Aldehyde combined as polyvinyl acetal 81.0 Ester as polyvinyl acetate 10.1 Alcohol as polyvinyl alcohol 7.2

A second resin was used and which was prepared by employing partially hydrolyzed polyvinyl acetate (formed from polyvinyl acetate having a viscosity of 15 centipoises when measured in a molar solution of benzene at 20 C.) and re-- acted'wilh acetaldehyde under suitable conditions and in the presence of a catalyst. An analysis of the resulting polyvinyl acetal resin showed that the polyvinyl acetate was hydrolyzed to the cxtent'o'f about 92% and that approximately 88% oi the alcohol or hydroxyl groups of the partially hydrolyzed polyvinyl acetate had combined with the acetaldehyde in the finished resin. On analysis, the resin showed:

. Percent Aldehyde combined as polyvinyl acetal 79.5 Ester as polyvinyl acetate 11.0 Alcohol as polyvinyl alcohol 8.1

Percent Aldehyde combined as polyvinyl acetal 81.2 Ester us polyvinyl acetate .57 Alcohol as polyvinyl alcohol 19.6

A great many plastics were made using as plasticizers the acid esters herein disclosed. As representative examples of some of the resin plastics, the following proportions and plasticizers are set forth.

In each'of the following ten examples, the resin used was the polyvinyl acetal resin in which formaldehyde was employed in the reaction, and the parts given are by weight:

Example 1: 100 parts resin 7 50 parts dimethyl adipate Example 2: 100 parts resin 50 parts diethyl adipate Example 3: 100 parts resin 50 parts dimethyl suberate 100 parts resin 50 parts diethyl suberate 100 parts resin 42.5 parts dimethyl phthalate 42.5 parts dimethyl sebacate 100 parts resin 50 parts dimethyl ester of decamethylene dicarboxylic acid 50 parts dimethyl ester of phthalic acid 100 parts resin 50 parts di (monoethyl ether of ethylene glycol) adipate 100 parts resin 50 parts di (monoethyl ether of ethylene glycol) suberate 100 parts resin 5 50 parts di (monoethyl ether of ethylene glycol) sebacate Example 10: 100 parts resin i 60 parts di (monoethyl ether of ethylene glycol) ester of decamethylene dicarboxylic acid Example 4:

Example 5:

Example 6:

Exam le 7:

Example 8:

Example 9:

The following examples are given in connection with the polyvinyl acetal resin in which butyraldehyde was employed during the reaction, and the parts specified are by weight:

Example 11: .100 parts resin 50 parts dimethyl adipate Example 12: 100 parts resin 50 parts diethyl adipate Example 13: 100 parts resin 50 parts dibutyl adipate Example 14: 100 parts resin parts dimethyl suberate Example 15: 100 parts resin 50 parts diethyl suberate Example 16: 100 parts resin 50 parts dibutyl suberate 50 Example 17: 100 parts resin 50 parts diamyl suberate Example 18: 100 parts resin 50 parts dimethyl sebacate Example 19: 100 parts resin 1 50 parts diethyl sebacate Example 20: 100 parts resin 50 parts dibutyl sebacate Example 21: 100 parts resin 50 parts di (monoethyl ether of ethylene glycol) sebacate Example 22: 100. parts resin 50.,Dartsdimethyl ester of decanithylene dicarboxylic acid v 1:; Example 23: 100 parts resin 50 parts diethyl ester of decamethylene dicarboxylic acid Example 24: 100 parts resin 50 parts dibutyl ester of decamethylene dicarboxylic acid The foregoing examples are not a complete list of all plasticizers comprehended by this in- .40 i plasticized with 50 parts of dibutyl ester of decamethylene dicarboxylic acid, it'had a critical disvention but are sufilcient to enable those versed in the art to practice theyinvention by following the teachings herein set forth.

Asrepresentative break test data, the follow--.

termine the critical distance at the temperatures 7 listed:

The polyvinyl acetalresin involving the use of formaldehyde, when plasticized with 50 parts of dimethyl adipate per 100 parts of resin, had a. critical distance at F. of 18 feet; at 70 F. of 1 --21 feet; and/at 120 F; of 9 feet. The same resin,

when plasticized with 42.5 parts dimethyl phthalate and 42.5parts dimet hyl sebacate per 100 parts of resin, had a critical distance at 0 F. of

16 feet; at 70 F.21 feet plus; at 120 F.-11 feet. 'Ifhe same resin, when plasticized with 50 I parts of dimethyl ester of decamethylene dicar- 1 boxylic acid and 50 parts of dimethyl phthalate per 100 parts of resin, had'a critical distance at 0 F. of 10 feet; at 70 F.-21 feet; and at 120 F.-8 feet.

The following resin plastics were made using polyvinyl acetal resin involving butyraldehyde 'in its formation and when 100 parts of said resin the'resin was plasticized with 50 parts of diamyl suberate per 100 parts of resin, it had a critical distance at 0 F. of 13 feet; at 70 F.--21 feet plus; and at 120 F.--9 feet. When 100 parts of resin was plasticized with 50 parts of dibutyl sebacate, it had a critical distance at 0 F. of 16 feet; at 70 l t-21% feet plus; and at 120 F. 8 to 10.feet. When 100 parts of the resin was tance at 0 F. of 14 feet; at 70 F.-21 feet;

and at 120 F.-8 feet.

percent of the available hydroxyl groups of saidhydrolysis product have been reacted with the aldehyde, and an ester of monohydric alcohol and astraight chain dicarboxylic acid having four or more methylene groups as a compatible Diasticizer for said polyvinyl acetal resin.

2. A synthetic resin plastic which comprises a I i polyvinyl acetal resin formed by the reaction of a saturated aldehyde on ,a partially or wholly hydrolyzed polyvinyl ester in which. at least sixty percent of the available hydroxyl groups of said hydrolysis product have been reacted with the al dehyde, an ester of monohydric alcohol and a straight chain dicarboxylic acid having four or more methylene groups as a compatible plasticizer for said polyvinyl acetal resin, and a compatible diluent plasticizer therefor.

3. A synthetic resin plastic which comprises a polyvinyl acetal resin formed by the reaction of a saturated aldehyde on a partially or wholly hydrolyzed polyvinyl ester in which at least sixty percent of the available hydroxyl groups of said hydrolysis product have been reacted with the aldehyde, an ester of monohydric alcohol and a straight chain dicarboxylic acid having four or more methylene groups as a compatible plasticizer for said polyvinyl acetal resin, and a compatible ester of phthalic acid.

4. A synthetic resin plasticwhich comprises a polyvinyl acetal resin formed by the reaction of a saturated aldehyde on a partially or wholly hydrolyzed polyvinyl ester in which at least sixty percent of the available hydroxyl groups of said hydrolysis product have been reacted with the aldehyde, anda methyl ester of a straight chain dicarboxylic acid having four to six methylene groups as a compatible plasticizer for said polyvinyl ac'etal resin.

5. A synthetic resin plastic which comprises a polyvinyl acetal resin formed by the reaction of a saturated aldehyde on a partially or wholly hydrolyzed polyvinyl ester in which at least sixty percent of the available hydroxyl groups of said hydrolysis product have been reacted with the aldehydeyand an ethyl ester of a straight chain dicarboxylic acid having four to six methylene groups as a compatible plasticizer for said polyvinyl acetal resin.

6. A synthetic resin plastic which comprises a polyvinyl acetal resin formed by the reaction of a saturated aldehyde having more than one carbon atom on a partially or wholly hydrolyzed polymerized vinyl ester in which at least sixty percent of the available hydroxyl groups of said hydrolysis product have been reacted with the r aldehyde, and an ester of monohydric alcohol and a straight chain dicarboxylic acid having four or more methylene groups as a compatible plasticizer for said polyvinyl acetal resin.

7. A synthetic resin plastic which comprises a polyvinyl acetal resin formed by the reaction of a saturated aldehyde having more than one carbon atom on a partially or whollyhydrolyzed polymerized vinyl ester in which at least sixty percent of the available hydroxyl groups of said hydrolysis product have been reacted with thealdehyde, an ester of monohydric alcohol and a straight chain dicarboxylic acid having four or more methylene groups as a compatible plasticizer for said polyvinyl acetal resin, and a compatible diluent plasticizer therefor.

JOSEPH D. RYAN. 

